The present invention relates to a cable including a cable jacket and at least two medium voltage wires disposed within the cable jacket for transporting medium voltage current and a wind turbine having a generator for generating electricity. It further relates to a wind park with at least two wind turbine generators.
Wind turbines are commonly used to convert kinetic energy of an air stream into electrical energy. They include a transformer to transform the generated low voltage electricity to a medium voltage, for delivering the energy via a medium voltage cable to a medium voltage grid. Under normal conditions a wind turbine generates enough energy for its internal use, e.g. to power an elevator, a crane or an illumination in a tower of the wind turbine to provide enough light for an engineer or technician inspecting the wind turbine. But, often the wind turbine has to be stopped for an inspection and the connection of the transformer to the grid has to be cut. Offshore wind turbines that are disconnected from the medium voltage collector system for repair or maintenance work cannot provide electrical power. In these cases an auxiliary power source has to be provided for most of the work, e.g. to power the elevator, the crane or the illumination.
For example in case of offshore wind turbines the auxiliary power must be generated in place, e.g. by a small generator placed in the tower that is powered by conventional fuels. The use of fuel based mobile generators is expensive in offshore applications and offshore wind turbines are often placed in protected landscape/environment such that strict regulations concerning the handling of fuel apply thereto, if it is allowed at all. A further possibility is to place an auxiliary generator on a boat and to connect the auxiliary power circuit in the wind turbine with the generator on the boat. In this case, it is difficult to connect the circuits under all weather conditions and this limits the possibilities for operation and maintenance works. If batteries are used as auxiliary power supplies for the illumination or the like, they have to be regularly replaced by new ones. Battery backup systems can be used for low power consuming equipment but will not provide enough power for most of the tools required for maintenance and repair jobs. Thus, batteries or mobile generator systems cause high costs mainly on the lifetime.